This invention relates to an apparatus for cooling integrated circuit chips and, in particular, to a circuit module which utilizes a liquid cooled film to extract heat from the upper surfaces of the chips.
The use of integrated circuit chips has increased dramatically over the years. Although chip size has decreased and power usage is more efficient than in the past, the practice of mounting multiple, closely spaced chips in modules has required that more emphasis be placed on cooling systems to remove the relatively high density power dissipated by the chips. Liquid coolants are commonly employed in high density applications. One problem associated with cooling integrated circuit chips mounted on a substrate is that some of the chips may be tilted or bent and otherwise may have height variations between chips. It is desirable that any cooling system accommodate slightly different chips orientations while providing approximately equal cooling to each chip site.
The prior art has suggested various systems for cooling high powered integrated circuit chips, including those in which multiple chips are arrayed in modules. Previous thermal conductive modules (TCMs) have utilized pistons contained in water cooled housings which contact the chip. Some systems have incorporated water cooled bellows to cool the chip. Such systems are exemplified by IBM Technical Disclosure Bulletin, Vol. 28, No. 11, pp 4759-4761 (April 1986). Another chip cooling arrangement is suggested in IBM Technical Disclosure Bulletin, Vol. 27, No. 1B, pp. 494-495 (June 1984) in which a copper structure having an internal radial water cooling pattern is conformally interfaced using a layer of a metal alloy with a single semi-conductor chip.
Other systems for cooling high powered chips utilize a cooled foil to cover a plurality of chips. One of such systems, disclosed in U.S. Pat. No. 4,381,032, uses a piston to hold the foil against each chip and a liquid coolant which flows around the piston to remove heat conducted through the foil. Another system which utilizes a heat conductive foil over the integrated circuit chips is disclosed in U.S. Pat. No. 4,531,146. IBM Technical Disclosure Bulletin, Vol. 29, No. 7, p. 2887 (December 1986) discloses yet another system which utilizes a metal heat sink carried on a flexible seal for each chip which is spring loaded downwardly against the chip. The upper surface of the heat sink carries fins and is cooled by a jet of coolant.
In a system disclosed in a recent patent issued to the assignee of this application, Chrysler et al. U.S. Pat. No. 4,928,207, the coolant is carried to each chip through the central bore of a piston which is space away from the chip by a spacer having radial vanes. However, this system uses a dielectric coolant which contacts the chips directly and is not suitable with aqueous coolants because of problems of corrosion and short circuiting of the chips.
Although these systems are suitable in many ways, many require their components to be made to high mechanical tolerances and, consequently, are relatively expensive. This is especially true of those systems employing pistons in thermal conduction modules which form part of the path for heat transfer. Furthermore, the power density of multiple chip modules is expected to increase dramatically, particularly as systems approach very large scale integration (VLSI) densities in bipolar technology. This will require even higher thermal conductance between the chip and the coolant, which prior systems may not be able to accommodate. The use of water based coolants is desirable in this regard. Furthermore, it is necessary that the cooling system be reliable, relatively low in cost to manufacture, and easily replaceable in the field.
Bearing in mind the problems and deficiencies in the prior art, and the requirements of new integrated chip technology, it is therefore an object of the present invention to provide a high performance cooling system for integrated circuit chips.
It is another object of the present invention to provide an integrated circuit chip cooling system which utilizes components made to relatively low mechanical tolerances.
It is yet another object of the present invention to provide an integrated circuit chip cooling system which utilizes a water base coolant which does not contact the chips themselves to protect them from corrosion and other problems.
It is a further object of the present invention to provide a cooling system for integrated circuit chips which are tilted, bent, or have chip-to-chip height variations without stressing the connection between the chip and the chip substrate.
It is another object of the present invention to provide a multiple chip cooling system in which equal cooling is provided at each chip site.
It is yet another object of the present invention to provide an integrated circuit chip cooling system which provides a high conductance thermal path between the chip and the coolant.